1. Field of the Disclosure
The disclosure relates in general to a display device and method of fabricating the same, and more particularly to an organic electroluminescent display (OELD) device and a method for fabricating the same.
2. Description of the Related Art
In comparison to the conventional cathode-ray tube display device, the flat panel display device (such as the liquid crystal display device (LCD), the plasma display device (PDP) and the organic electroluminescent display (OELD) device), being lighter, slimmer and compacter, has gradually become the mainstream product. Particularly, the OELD device further has the advantages of flexibility, portability, full color, high brightness, lower power consumption, wider view-angle and faster response rate.
Currently, the monochromic OLED technique is near matured. Considering the next generation flat display and the applications using the same, the full color OLED technique is an inevitable trend. Currently, there are three full color OLED techniques available. According to the first technique, the RGB sub-pixels required for full color are implemented by three independent elements. According to the second technique, the light of blue light OLED is converted into RGB lights by a color change medium (CCM). According to the third technique, the light of white light OLED is converted into RGB lights by a plurality of color filters. Each technique has its advantages and disadvantages. The third technique implements a full color OLED by using a white light element plus color filters. Since the color filter technique is already matured in the LCD industry, it is not difficult to find RGB color filters applicable to the white light OLED and further transfer the technique to the OLED industry. Furthermore, the fabricating procedures for the white light OLED plus color filters are relatively simple, and the fabricating cost for full color OLED can thus be further reduced.
FIG. 1 shows a partial cross-sectional view of a generally known OELD device. The OELD device is formed mainly by an organic light emitting diode (OLED) assembly 10 and a color filter (CF) assembly 20. The OLED assembly 10 and the CF assembly 20 are assembled to each other, and the cell gap between the two assemblies is controlled by plural spacers 30. The OLED assembly 10 includes a first substrate 101 with thin-film transistor units. The organic electroluminescent unit 103, interposed between two electrodes such as a reflective electrode and a transparent electrode (the electrodes are not illustrated in the diagram), is formed on the first substrate 101 with thin-film transistor units. The generally known method for fabricating the CF assembly 20 includes the following steps. A glass substrate 201 is pre-treated, such as treated by a cleaning process. A photolithography process is applied on the pre-treated glass substrate 201 to form a patterned light-shielding layer 203, such as a black matrix (BM). A color filter layer 205 is formed by sequentially forming a red color filter layer CF-R, a green color filter layer CF-G and a blue color filter layer CF-B. Then, an overcoat (OC) layer 207 is formed to cover the color filter layer 205. Since the thicknesses of the red, the green and the blue color filter layers are not the same, planarization of the overcoat layer 207 on the red, the green and the blue color filter layers could be achieved. A plurality of spacers 30 may be formed on the overcoat layer 207. After the OLED assembly 10 and the CF assembly 20 are assembled with each other, the spacers 30 maintain a cell gap between the two assemblies. However, the disposition of the overcoat layer 207 and the spacers 30 increases the overall thickness of the display device, so that color shift may occur at a smaller angle. In addition, when the spacers are disposed beside one of the red, the green and the blue color filter layers, the width of the black matrix for the particular color is increased, and the aperture ratio for the particular color is reduced.